CSS sliding underline effect on hover

index.html

<h1><a href="#" class="slide-left-right">Sliding from left to right</a></h1>
<h1><a href="#" class="slide-right-left">Sliding from left to right</a></h1>
<h1><a href="#" class="slide-center-out">Sliding from center to left and right sides</a></h1>
<h1><a href="#" class="slide-in-out">Sliding in from left and sliding out to the right</a></h1>